Chinese language Hackers Backdoored MiMi Chat App to Goal Home windows, Linux, macOS Customers


A pair of experiences from cybersecurity corporations SEKOIA and Development Micro sheds mild on a brand new marketing campaign undertaken by a Chinese language risk actor named Fortunate Mouse that entails leveraging a trojanized model of a cross-platform messaging app to backdoor programs.

An infection chains leverage a chat utility known as MiMi, with its installer recordsdata compromised to obtain and set up HyperBro samples for the Home windows working system and rshell artifacts for Linux and macOS.

As many as 13 totally different entities situated in Taiwan and the Philippines have been on the receiving finish of the assaults, eight of whom have been hit with rshell. The primary sufferer of rshell was reported in mid-July 2021.

Fortunate Mouse, additionally known as APT27, Bronze Union, Emissary Panda, and Iron Tiger, is thought to be lively since 2013 and has a historical past of getting access to focused networks in pursuit of its political and army intelligence-collection goals aligned with China.


The superior persistent risk actor (APT) can be adept at exfiltrating high-value data utilizing a variety of customized implants comparable to SysUpdate, HyperBro, and PlugX.

The most recent growth is important, not least as a result of it marks the risk actor’s introductory try at focusing on macOS alongside Home windows and Linux.

MiMi Chat App

The marketing campaign has all of the hallmarks of a provide chain assault in that the backend servers internet hosting the app installers of MiMi are managed by Fortunate Mouse, thus making it potential to tweak the app to retrieve the backdoors from a distant server.

That is borne out by the truth that the app’s macOS model 2.3.0 was tampered to insert the malicious JavaScript code on Might 26, 2022. Whereas this may occasionally have been the primary compromised macOS variant, variations 2.2.0 and a couple of.2.1 constructed for Home windows have been discovered to include comparable additions as early as November 23, 2021.

rshell, for its half, is an ordinary backdoor that comes with all the same old bells-and-whistles, permitting for the execution of arbitrary instructions acquired from a command-and-control (C2) server and transmitting the outcomes of the execution again to the server.


It is not instantly clear if MiMi is a professional chat program, or if it was “designed or repurposed as a surveillance software,” though the app has been utilized by one other Chinese language-speaking actor dubbed Earth Berberoka (aka GamblingPuppet) aimed toward on-line playing websites – as soon as once more indicative of the prevalent software sharing amongst Chinese language APT teams.

The operation’s connections to Fortunate Mouse stems from hyperlinks to instructure beforehand recognized as utilized by the China-nexus intrusion set and the deployment of HyperBro, a backdoor completely put to make use of by the hacker group.

As SEKOIA factors out, this isn’t the primary time the adversary has resorted to using a messaging app as a jumping-off level in its assaults. In late 2020, ESET disclosed {that a} widespread chat software program known as In a position Desktop was abused to ship HyperBro, PlugX, and a distant entry trojan known as Tmanger focusing on Mongolia.


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